WO2017097748A1 - Composition and rodenticide bait comprising difethialone and method for controlling target rodent pests - Google Patents

Abstract

The invention relates to a composition comprising diféthialone, characterised in that it contains a configurational stereoisomer of difethialone, referred to as a hetero-stereoisomer, of formula 3-(4'-bromobiphenyl-4-yl)-1-(4-hydroxythiocoumarin-3-yl)-1,2,3,4-tetrahydronaphthalene, in which the carbon atoms 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group have different absolute configurations, said composition comprising an amount of a dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the amount of diféthialone in the composition is less than 10%; the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone in the composition being different from the amount of levorotatory enantiomer of said hetero-stereoisomer of difethialone in the composition.

Description

 COMPOSITION AND RODONTICIDE BAIT COMPRISING DIFETHIALONE, METHOD FOR CONTROLLING RODENTS

 HARMFUL TARGETS

 The invention relates to a composition comprising difethialone, a rodenticide bait comprising such a composition and a method for controlling harmful target rodents. The invention thus relates to the technical field of the fight against target rodent pest populations.

 It is known to use rodenticide baits as a poison for harmful target rodents. It is known from EP 2,090,164 that difethialone is a second-generation anticoagulant acting at a single dose. US 2005/181003 discloses a rodenticide bait in gel form comprising difethialone in a mass proportion of 25 ppm.

 Such bait is likely to be consumed by animals other than harmful target rodents when made available to harmful target rodents. It can be consumed directly (primary consumption) by pets or pets. It can also be accidentally consumed by humans. Such consumption may produce poisoning in these pets, pets, or humans that can be lethal.

 In addition, a fraction of the difethialone of these rodenticide baits may be ingested (secondary consumption) by animals - in particular by weaker rodent-killing predatory birds that have consumed such a rodenticide bait or by dead rodent-killing scavenging animals. have consumed such rodenticide bait. This secondary consumption is likely to eventually lead to the death of these predatory animals or scavengers that may be animals - especially birds - belonging to protected species.

The invention therefore aims to overcome these disadvantages by proposing a composition comprising difethialone, a rodenticide bait comprising such a composition and a rodent control method. harmful targets that are at the same time effective in controlling target rodent pest populations, but which also limit the risk of poisoning non-target animals - especially domestic animals, pets or humans - accidentally such bait rodenticide and the risks of poisoning by secondary consumption of domestic animals (pets or farm animals) or wild -for example foxes or birds - predators rodent harmful target having consumed rodenticide bait or scavengers dead target rodents poisoned.

 The invention also aims at providing a composition comprising difethialone, a rodenticide bait comprising such a composition and a method for controlling harmful rodent rodents whose implementation is in accordance with the rules of good practice-especially with respect to the protection of birds, especially raptors.

 The invention is also directed to a composition comprising difethialone, a rodenticide bait comprising such a composition and a method of controlling deleterious target rodents that require only low doses of difethialone to control a rodent susceptible and respectful rodent population. environment, human health and non-target animals - especially birds.

 The invention also aims at providing a composition comprising difethialone, a rodenticide bait comprising such a composition and a method for controlling harmful target rodents that are likely to be used to control harmful target rodents resistant to known baits. to control harmful target rodents.

 The invention also aims at providing an alternative to rodenticide agents and known rodenticide baits.

To this end, the invention relates to a composition comprising difethialone, characterized in that it comprises a configuration stereoisomer of the difethialone, called hetero-stereoisomer, of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein carbons 1 and 3 of the 1,2,3 group, 4-Tetrahydronaphthalene are of distinct absolute configurations (1R, 3S or 1S, 3R), said composition comprising an amount of dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the amount of the difethialone in the composition is less than 10%;

the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the composition being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the composition.

 Throughout the text:

 the term "difethialone" refers to the compound 3- (4'-bromobiphenyl-

4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene or 3- [3- [4- (4-bromophenyl) phenyl] -1-tetralinyl] -2- hydroxy-4-thiochromenone, or 3- [3- (4'-bromo [1,1'-biphenyl] -4-yl) -1,2,3,4-tetrahydro-1-naphthalenyl] -4-hydroxy- 2H-1-benzothiopyran-2-one, of formula I) below:

in which the numbers of carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are presented;

the term "stereoisomers" refers to isomers of the same semi-expanded formula, but whose relative position of atoms differs in space. The term "configuration stereo-isomers" refers to stereoisomers whose conversion of these configuration stereoisomers into one another requires a break / reformation of an interatomic covalent bond. Thus, the term "configuration stereo-isomers" refers to stereoisomers which are not conformational isomers (or "rotamers", whose conversion of the one to the other of the conformational isomers is accompanied only by a rotation of a part of the molecule along the axis a bond σ (sigma) formed by axial overlap of orbitals);

 the term "hetero-stereoisomer" of difethialone refers to the configuration stereoisomer of the difethialone of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) - 1, 2,3,4-tetrahydronaphthalene, wherein carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene moiety of said hetero-stereoisomer are of distinct absolute configurations (1R, 3S and 1S, 3R), said absolute configurations being determined according to the sequential priority rules and nomenclature of Cahn, Ingold and Prelog (CIP);

 the term "homo-stereoisomer" of difethialone refers to the configuration stereoisomer of the difethialone of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) - 1,2,3,4-tetrahydronaphthalene, wherein carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene moiety of said homo-stereoisomer are of the same absolute configuration (1R, 3R and 1S, 3S), and ;

 the term "quantity" means a molar amount, a mass quantity or a volume quantity. The proportions are therefore proportions of a molar amount relative to a molar amount, of a mass quantity relative to a mass quantity, or of a volume quantity referred to a volume quantity;

 the term "substantially" indicates, in the usual way, that a structural or functional feature should not be taken as marking an abrupt discontinuity, which would have no physical meaning, but covers not only that structure or function, but also slight variations of this structure or function which produce, in the technical context considered, an effect of the same nature, if not of the same degree;

the terms "high pressure liquid chromatography" or "high performance liquid chromatography"("HPLC") refer to "HPLC" or "High Performance Liquid Chromatography" chromatography, and; the term "retention time" refers to the duration, measured at the peak of the chromatogram peak, during which a compound is retained on a chromatography column.

 In a composition according to the invention:

said hetero-stereoisomer of difethialone is present in the form of a quantity Q _D of a dextrorotatory enantiomer and a quantity Q _L of a levorotatory enantiomer, and;

said homo-stereoisomer of difethialone is present in the form of a quantity Q ' _D of a dextrorotatory enantiomer and a quantity Q' _L of a levorotatory enantiomer.

 In this composition, the proportion:

 QD

QD + QL + Q 'D + Q' L

is greater than or equal to 0 and strictly less than 10%, with Q _L ≠ Qj

 A composition according to the invention comprises an amount of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone such that the ratio of this amount to the amount of the difethialone is less than 10%, excluding a composition comprising:

 an amount of said homo-stereoisomer of the difethialone such that the ratio of this amount to the amount of difethialone (total) in the composition is between 80% -included and 100% -borne inclusive, and;

 an amount of a racemic mixture of enantiomers of said hetero-stereoisomer of difethialone such that the ratio of this amount to the amount of difethialone (total) in the composition is between 0% -borne and 20%; Excluded terminal.

A composition according to the invention may be free of dextrorotatory enantiomer of said hetero-stereoisomer of difethialone. The composition may also comprise the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone in trace form. Such a substantially dextrorotatory enantiomerically free composition of said difethialone hetero-stereoisomer comprises a non-zero proportion of laevorotatory enantiomer of said hetero-stereoisomer of difethialone. The inventors have succeeded in separating the levorotatory and dextrorotatory enantiomers of said hetero-stereoisomer from difethialone and the levorotatory and dextrorotatory enantiomers of said homo-isomer of difethialone by high-pressure liquid chromatography in isocratic mode and under specific conditions. using a chromatography column comprising a chiral stationary phase. It was in fact not known at the time of the invention to be able to separate the levorotatory and dextrorotatory enantiomers of said homo-isomer of difethialone and the levorotatory and dextrorotatory enantiomers of said hetero-stereoisomer of difethialone.

 They were able to achieve this separation using a column

HPLC LUX ^® Cellulose-3 (Phenomenex, Le Pecq, France) of dimension 150 x 2 mm and comprising a chiral stationary phase consisting of porous particles of cellulose tris (4-methylbenzoate), a particle size of 3 μπι and a porosity of 1000 A and, as a mobile phase, an eluent obtained by mixing acetonitrile (A) and water comprising formic acid in a volume proportion of 0.1% in water (B), the A / B volume ratio being 80/20. The flow rate of the mobile phase in the column is maintained at a value of 0.25 ml / min and the separation is carried out at a temperature of 23.2 ° C. The composition to be analyzed is at a concentration of 1 μg of difethialone per milliliter of acetonitrile and the volume injected into the column is 1 μl ·. Detection is performed by tandem mass spectrometry (MS / MS) or spectrophotometry by adjusting the difethialone concentration and injection volume for optimal detection.

Under these conditions, the value of the retention time (t ₃ ) of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone can vary according to the operating conditions - in particular according to the temperature conditions of the column - and be between , 3 min and 11.8 min. The value of the retention time (t ₂ ) of the laevorotatory enantiomer of said hetero-stereoisomer of difethialone may vary according to the operating conditions - in particular according to the temperature conditions of the column - and be between 9.0 min and 9.5 min, so the dextrorotatory and levorotatory enantiomers of said hetero-stereoisomer can be separated by high pressure liquid chromatography on a chiral column.

The value of the retention time (ti) of the laevorotatory enantiomer of said ho-stereo-isomer may vary according to the operating conditions - in particular according to the temperature conditions of the column - and be between 7.8 min and 8.2 min. The value of the retention time (t ₄ ) of the dextrorotatory enantiomer of said homo-stereoisomer according to the invention may vary according to the operating conditions - in particular according to the temperature conditions of the column - and be between 14.0 min. and 14.4 min. so that the dextrorotatory and laevorotatory enantiomers of said homo-isomer can be separated by high pressure liquid chromatography on a chiral column.

Thus, under these analytical conditions, the elution order of the configuration stereoisomers of the difethialone is such that t <t ₂ <t ₃ <t ₄ . The values of the retention times t ₁₅ t ₂ , t ₃ and t are likely to vary, in particular according to the chromatography conditions and according to the temperature of the chromatography column. However, under these chromatographic conditions, the order of elution of the configuration stereoisomers of the difethialone remains unchanged.

 The amount of each configuration isomer of the difethialone is measured from a chromatogram by evaluating the area under the peak corresponding to each enantiomer and, if applicable, comparing this area measure with the areas obtained by sample analysis comprising known amounts of configuration stereoisomers of the difethialone.

 Rotational power of configuration stereoisomers

The rotational power of each of the configuration stereoisomers of difethialone in solution in chloroform (CHCt ₃ ) is measured by means of a P 2000 digital polarimeter (JASCO, Bouguenais, France) operating with an excitation light of wave of 589 nm.

The mean rotatory power (calculated over two series of ten measurements) of a dextrorotatory enantiomer solution of said homo-stereoisomer of difethialone at 11.6 g / L in chloroform is 2.308 °. The specific rotation power at 25 ° C. [a] ₅₈ μm of the dextrorotatory enantiomer of said homo-stereoisomer of difethialone, measured on the sodium D line (589 nm), is + 19.9 °.

The average rotatory power (calculated on two series of ten measurements) of a levorotatory enantiomer solution of said homo-stereoisomer of difethialone at 11.05 g / L in chloroform is -1.635 °. The specific rotatory power at 25 ° C. [α] ^{25 C} 5 ₈ 9 _nm of the laevorotatory enantiomer of said homo-isomer of difethialone, measured on the sodium D line (589 nm) is -14.8 ° .

The average rotatory power (calculated over two series of ten measurements) of a dextrorotatory enantiomer solution of said hetero-stereoisomer of difethialone at 6.3 g / L in chloroform is + 0.573 °. The specific rotatory power at 25 ° C [α] ^{25 C} 5 ₈ 9 _nm of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone, measured on the sodium D-line (589 nm) is + 9.1 ° .

The average rotatory power (calculated on two series of ten measurements) of a laevorotatory enantiomer solution of said hetero-stereoisomer of 6.3 g / L difethialone in chloroform is -0.904 °. The specific rotation power at 25 ° C [α] ^{25 C} 5 ₈ 9 _nm of the laevorotatory enantiomer of said hetero-stereoisomer of difethialone, measured on the sodium D-line (589 nm) is -13 °.

 Circular Dichroism of Configuration Stereoisomers The dextrorotatory enantiomer of said homo-stereoisomer of difethialone dissolved in methanol at a concentration of 0.96 g / L and placed in a quartz tank for spectrophotometer, has a spectrum of circular dichroism produced at 25 ° C positive circular dichroism values between 220 nm and 300 nm.

The laevorotatory enantiomer of said homo-stereoisomer of difethialone dissolved in methanol at a concentration of 0.81 g / L and placed in a quartz tank for spectrophotometer, has a circular dichroism spectrum produced at 25 ° C. negative circular dichroism values between 220 nm and 300 nm.

The dextrorotatory enantiomer of said hetero-stereoisomer of difethialone dissolved in methanol (CH ₃ OH) at a concentration of 0.65 g / L and placed in a quartz tank for spectrophotometer, has a circular dichroism spectrum realized at 25 ° C positive circular dichroism values between 210 nm and 250 nm and between 270 nm and 300 nm.

 The laevorotatory enantiomer of said hetero-stereoisomer of difethialone dissolved in methanol at a concentration of 0.94 g / L and placed in a quartz tank for spectrophotometer, has a circular dichroism spectrum produced at 25 ° C. negative circular dichroism values between 225 nm and 250 nm.

 Proton nuclear magnetic resonance

Said homo-stereoisomer of difethialone exhibited in nuclear magnetic resonance spectroscopy (1H NMR) of the 300 MHz proton in CDCt ₃ a multiplet having a chemical shift (δ) of between 4.9 ppm and 5.1 ppm corresponding carbon 1 of the 1,2,3,4-tetrahydronaphthalene group of said homo-stereoisomer of difethialone. The levorotatory and dextrorotatory enantiomers of said homo-stereoisomer of difethialone are not distinguishable by proton NMR.

Said hetero-stereoisomer of difethialone exhibited in nuclear magnetic resonance spectroscopy (1H NMR) of the 300 MHz proton in CDCt ₃ a multiplet exhibiting a chemical shift (δ) of the order of 5.3 ppm corresponding to carbon 1 of the 1,2,3,4-tetrahydronaphthalene group of said homo-stereoisomer of difethialone. The levorotatory and dextrorotatory enantiomers of said hetero-stereoisomer of difethialone are not distinguishable by proton NMR.

The inventors who have succeeded in separating the configuration stereoisomers of difethialone have observed, in a totally surprising manner, that the configuration stereoisomers of difethialone do not exhibit the same liver remanence in harmful target rodents and that the enantiomer dextrorotatory of said hetero-stereoisomer of the difethialone has a hepatic persistence in harmful target rodents that is higher than that of the levorotatory enantiomer of said hetero-stereoisomer of difethialone and higher than that of the dextrorotatory and laevorotatory enantiomers of said homo-stereoisomer of difethialone.

 The dextrorotatory enantiomer of said hetero-stereoisomer of difethialone persists in the liver of harmful target rodents longer than the other enantiomers so that a dead or live harmful target rodent having ingested the dextrorotatory enantiomer of said hetero-stereoisomer difethialone is a poisonous prey for non-rodent mammals and birds consuming the harmful target rodent-dead or alive-and especially for predators (including non-rodent mammals and birds) that consume preferentially the viscera of their preys and in particular the liver of their preys.

 The inventors have also observed that a composition and rodenticide bait according to the invention having a dextrorotatory enantiomer amount of said hetero-stereoisomer of reduced difethialone and such that the ratio of this amount to the amount of difethialone is less than 10% - said dextrorotatory enantiomer of said hetero-stereoisomer of difethialone being the enantiomer of higher hepatic persistence - in fact makes it possible, and in a totally surprising manner, to effectively fight against harmful target rodents.

 The invention therefore relates to a composition and a rodenticide bait comprising difethialone wherein the amount of the configuration stereoisomer of the difethialone of higher hepatic persistence in rodents harmful target is such that the ratio of this amount to the amount of difethialone is less than 10%.

Advantageously and according to the invention, the composition comprises an amount of dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount of dextrorotatory enantiomer of said heterois stereoisomer to the (total) amount of the difethialone is less than at 9%, especially less than 7%, preferably less than 5%, more preferably less than 4%, even more preferably less than 3%. Advantageously and according to the invention, the composition may comprise an amount of dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount of dextrorotatory enantiomer of said hetero-stereoisomer to the total amount of the difethialone is less than 2%, in particular less than 1%.

 Advantageously and alternatively according to the invention, the composition may comprise a quantity of laevorotatory enantiomer of a configuration stereoisomer of the difethialone, called a ho-mono-isomer, of formula 3- (4'-bromobiphenyl-4 -yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of the same absolute configuration ( 1S, 3S or 1R, 3R), the amount of said laevorotatory enantiomer of said homo-isomer in the composition being such that the ratio of this amount to the total amount of the difethialone in the composition is less than 10%.

 The inventors who managed to separate the configuration stereoisomers of the difethialone also determined that the laevorotatory enantiomer of said homo-stereoisomer of the difethialone is in fact the enantiomer of the homo-stereoisomer of the difethialone which has the highest hepatic persistence in target rodent pests. They also observed that the levorotatory enantiomer of said homo-stereoisomer of difethialone is the most remanent in the rodent target rodent liver among the enantiomers of said homo-stereoisomer of difethialone and the laevorotatory enantiomer of said hetero-stereo isomer of difethialone.

Advantageously and according to this variant of the invention, the composition may comprise a quantity of laevorotatory enantiomer of said homo-stereoisomer such as the ratio of this amount of levorotatory enantiomer of said homo-stereoisomer to the total amount of the difethialone. is less than 9%, especially less than 7%, preferably less than 5%, more preferably less than 4%, even more preferably less than 3%. Advantageously and according to the invention, the composition comprises an amount of levorotatory enantiomer of said homo-stereoisomer such as the ratio of this amount. of the laevorotatory enantiomer of said homo-stereoisomer on the total amount of the difethialone is less than 2%, in particular less than 1%. The composition may also be free of the levorotatory enantiomer of said homo-stereoisomer of difethialone. The composition may also comprise the laevorotatory enantiomer of said homo-stereoisomer of difethialone in trace form in the composition.

 Advantageously and in another variant according to the invention, the composition may comprise a quantity of laevorotatory enantiomer of a configuration stereoisomer of the homo-stereoisone difethialone of formula 3- (4'-bromobiphenyl- 4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of the same absolute configuration (1S, 3S or 1R, 3R), the amount of said homo-stereoisomer being such that the ratio of this amount to the total amount of the difethialone in the composition is between 10% (inclusive) and 100% (terminal inclusive), in particular between 30% and 100%, in particular between 90% and 100%.

 Advantageously and alternatively according to the invention, the composition may also comprise an amount of levorotatory enantiomer of said hetero-stereoisomer of difethialone in the composition such that the ratio of this amount to the total amount of the difethialone in the composition is less than 10%.

The inventors who have succeeded in separating the configuration stereoisomers of difethialone and who have observed that the configuration stereoisomers of difethialone do not exhibit the same liver remanence in harmful target rodents, have also determined that the enantiomer the levorotatory of said hetero-stereoisomer of difethialone is in fact the most persistent enantiomer in the target rodent liver of the levorotatory enantiomer of said hetero-stereoisomer of difethialone and the dextrorotatory enantiomer of said hetero-stereoisomeric isomer of difethialone. Advantageously and according to this variant of the invention, the composition may comprise an amount of levorotatory enantiomer of said hetero-stereoisomer such as the ratio of this amount of laevorotatory enantiomer of said hetero-stereoisomer to the total amount of the difethialone is less than 9%, especially less than 7%, preferably less than 5%, more preferably less than 4%, even more preferably less than 3%. Advantageously and according to the invention, the composition comprises an amount of levorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount of laevorotatory enantiomer of said hetero-stereoisomer to the total amount of the difethialone is less than 2. %, in particular less than 1%. The composition may also be free from the laevorotatory enantiomer of said hetero-stereoisomer of difethialone, that is to say that the laevorotatory enantiomer of said hetero-stereoisomer of difethialone may be present in the composition but only at the state of traces.

 Advantageously and according to another variant of the invention, the composition may comprise an amount of the levorotatory enantiomer of said hetero-stereoisomer of difethialone such that the ratio of this amount to the total amount of the difethialone is between 10% (included terminal) and 100% (including terminal), in particular between 30% and 100%, in particular between 90% and 100%.

 Advantageously and alternatively according to the invention, the composition may comprise an amount of dextrorotatory enantiomer of said homo-stereoisomer of difethialone such that the ratio of this amount to the total amount of the difethialone in the composition is less than 10% .

However, nothing prevents that, advantageously and alternatively according to the invention, the composition may comprise an amount of dextrorotatory enantiomer of said homo-stereoisomer of difethialone such as the ratio of this amount to the total amount of difethialone in the composition is between 10% (inclusive) and 100% (inclusive), in particular between 30% and 100%, in particular between 90% and 100%. Advantageously and according to the invention, the composition is in the liquid state and comprises a liquid solvent of difethialone. It can also be a suspension or an emulsion of difethialone in a liquid medium.

 The invention also relates to the use of a composition according to the invention for the preparation of a rodenticide bait for harmful target rodents.

 The invention also relates to a rodenticide bait comprising a composition according to the invention, and at least one edible excipient for harmful target rodents.

 The invention thus relates to a rodenticide bait comprising difethialone and at least one edible carrier for harmful target rodents, characterized in that it comprises a stereoisomer of configuration of the difethialone, called hetero-stereoisomer, of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein carbons 1 and 3 of the 1,2,3 group, 4-Tetrahydronaphthalene are of distinct absolute configurations (1R, 3S or 1S, 3R), the rodenticide bait comprising an amount of dextrorotatory enantiomer of said hetero-stereoisomer such as the ratio of this amount to the amount of the difethialone in the Rodenticide bait is less than 10%;

the amount of dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait.

 Advantageously, a rodenticide bait according to the invention comprises an amount of dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the total amount of the difethialone in the rodenticide bait is less than 10% and the excluding a racemic mixture of the dextrorotatory and laevorotatory enantiomers of said hetero-stereoisomer of difethialone.

Advantageously and alternatively according to the invention, the rodenticide bait comprises a stereoisomer of configuration of the difethialone, said homo-stereoisomer of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein carbons 1 and 3 1,2,3,4-tetrahydronaphthalene group are of the same absolute configuration (1S, 3S or 1R, 3R), the rodenticide bait comprising an amount of a laevorotatory enantiomer of said homo-stereoisomer of difethialone such as the ratio of the amount of laevorotatory enantiomer of said homo-stereoisomer of difethialone to the total amount of the difethialone in the rodenticide bait is less than 10%.

 Advantageously and alternatively according to the invention, a rodenticide bait comprising difethialone according to the invention comprises:

 an edible carrier for harmful target rodents, and; an amount of the dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the total amount of the difethialone in the rodenticide bait is less than 10%, and

 an amount of the laevorotatory enantiomer of said homo-stereoisomer such that the ratio of the amount of laevorotatory enantiomer of said homo-stereoisomer to the total amount of the difethialone is less than 10%.

 Advantageously and according to the invention, the rodenticide bait comprises an amount of a laevorotatory enantiomer of said hetero-stereoisomer of difethialone such as the ratio of the amount of the laevorotatory enantiomer of said hetero-stereoisomer of difethialone in the rodenticide bait on the total amount of difethialone in the rodenticide bait is less than 10%.

 Advantageously and alternatively, a rodenticide bait according to the invention comprises:

 an edible carrier for harmful target rodents, and an amount of the dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the amount of the difethialone in the rodenticide bait is less than 10%, and;

an amount of the levorotatory enantiomer of said homo-stereoisomer such as the ratio of the amount of laevorotatory enantiomer of said homo-stereoisomer; stereoisomer on the amount of difethialone in the rodenticide bait is less than 10%, and;

 an amount of the laevorotatory enantiomer of said hetero-stereoisomer of the difethialone such that the ratio of that amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone to the amount of the difethialone in the rodenticide bait is less than 10%.

 Advantageously and according to the invention, the rodenticide bait comprises a mass quantity of difethialone such that the ratio (mass proportion) of this mass quantity of difethialone to the mass quantity of the rodenticide bait is less than 200 ppm-that is that is, less than 200 mg of difethialone per kilogram of rodenticide bait. Advantageously, the mass proportion of the difethialone is between 1 ppm and 200 ppm (1 mg to 200 mg of difethialone per kilogram of rodenticide bait), especially between 1 ppm and 100 ppm (1 mg to 100 mg of difethialone per kilogram rodenticide bait), preferably between 5 ppm and 50 ppm (5 mg to 50 mg of difethialone per kilogram of rodenticide bait), more preferably between 5 ppm and 25 ppm (5 mg to 25 mg of difethialone per kilogram). rodenticide bait), more preferably of the order of 15 ppm (15 mg of difethialone per kilogram of rodenticide bait).

 Advantageously and according to the invention, the edible excipient for harmful rodent targets is chosen to allow consumption of the bait by harmful target rodents. Advantageously and according to the invention, each edible excipient is non-lethal for harmful target rodents. The edible carrier is not a rodenticide in itself.

Advantageously and according to the invention, the edible excipient comprises at least one food selected from the group consisting of cereal seeds-notably dehulled cereal seeds-cereal seed mills, cereal seed flours, flakes cereal seed, cereal bran and non-cereal seeds, eg alfalfa seed - in particular in shell form, in the form of in the form of flour, in the form of flakes or bran. The edible carrier may include any carrier that may be consumed by harmful target rodents.

 Advantageously, the edible carrier comprises at least one food selected from the group consisting of plant foods and foods of animal origin. Advantageously, the edible carrier comprises at least one food chosen to stimulate the appetite of harmful target rodents. In particular, this food is selected from the group consisting of seeds of one or more cereals, seeds of one or more grains, seeds of one or more grains, seed flakes of one or more cereals, the sound of one or more cereals, and the grain meal of one or more cereals. For example, cereals are selected from the group consisting of oats, wheat, barley, corn, soybeans and rice.

 Advantageously, the food is selected from the group consisting of sweet foods. For example, these may be foods comprising at least one sugar selected from the group consisting of sucrose, lactose, fructose and glucose. It may be a sugar syrup-for example, a sugar syrup obtained by hydrolysis of the starch-or a sugar syrup obtained by hydrolysis of sucrose (invert sugar syrup), or beet sugar syrup, or maple syrup or sugar cane syrup, or syrup obtained from a plant of the genus stevia.

 Advantageously, the food is chosen from the group consisting of flakes and coconut albumen flour (copra). Advantageously, the food is selected from the group consisting of nuts, hazelnuts and almonds-shredded and / or powdered.

Advantageously, the food is selected from the group consisting of vegetable fats, vegetable oils (for example rapeseed oil, soy fat, sunflower oil, cocoa butter, peanut oil, peanut butter, corn oil palm oil), animal fats and animal oils (butter, lard, fish oil). Advantageously, the food is selected from the group consisting of proteins of plant origin and proteins of animal origin. By way of example, mention may be made, for example, of powdered milk, particularly powdered skimmed milk, eggs, in particular powdered eggs, protein hydrolysates of animal origin and protein hydrolysates of origin. vegetable.

 Advantageously and according to the invention, the rodenticide bait is chosen from the group consisting of solid baits comprising difethialone and a solid edible excipient. Advantageously, the rodenticide bait is a solid in the divided state, for example in the form of pellets or granules. Advantageously, the rodenticide bait can be a solid in the form of a block or paste that can be consumed by the target harmful rodents or a solid material that can be eaten by the target harmful rodents. Advantageously, the solid rodenticide bait according to the invention can be in the form of a rigid block, a semi-rigid block, a foam, a powder or a gel.

 Advantageously, the rodenticide bait in the form of a powder, in the form of a foam or in the form of a gel is adapted to be able to soil the fur of the target rodent (s) harmful (s) ) and to be ingested by him (them) during his (their) grooming.

 Advantageously and according to the invention, the rodenticide bait is chosen from the group consisting of liquid baits comprising difethialone and a liquid edible excipient. The rodenticide bait is then a drink for harmful target rodents. It may be a solid difethialone suspension in a liquid edible carrier or a difethialone emulsion in a liquid medium.

 Advantageously, the rodenticide bait comprises at least one dye. Such a dye makes it possible in particular to give said rodenticide bait a color easily detectable and identifiable by a person handling the rodenticide bait.

Advantageously, the rodenticide bait comprises at least one preservative able to ensure its conservation during storage. Advantageously, the rodenticide bait includes at least one bittering type compound denatonium benzoate, also known as the "Bitrex ^®" designed to reduce the risk of accidental consumption by non-target organisms.

 Advantageously, in a particular variant, the composition and the rodenticide bait according to the invention comprise exclusively difethialone as a rodenticide substance. In particular, the composition and the rodenticide bait according to the invention are free of any other anticoagulant substance for rodenticide use. However, in this variant according to the invention, the composition and rodenticide bait may include any harmful substance other than a rodenticide, such as an insecticide and / or acaricide.

 Advantageously, in another particular variant, the composition and the rodenticide bait according to the invention comprise difethialone and at least one other substance distinct from the difethialone as rodenticide substance. This other rodenticide substance, distinct from difethialone, may be another anticoagulant, particularly vitamin K or non-vitamin K, or another non-anticoagulant rodenticide.

 The invention also relates to a method for controlling harmful target rodents in which a quantity of rodenticide bait according to the invention is dispersed.

 The invention thus relates to a method for controlling harmful target rodents in which a quantity of rodenticide bait comprising difethialone is dispersed, and:

 at least one edible carrier for harmful target rodents, and

a stereoisomer of configuration of the hetero-stereoisomeric difethialone of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3 , 4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of distinct absolute configurations (1R, 3S or 1S, 3R), the rodenticide bait comprising an amount of a dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the amount of the difethialone in the rodenticide bait is less than 10%;

the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait.

 The invention also relates to a method for controlling harmful target rodents in which a quantity of rodenticidal bait according to the invention is dispersed comprising an amount of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone in a proportion of less than 10. % relative to the amount of difethialone, the amount of bait being sufficient to be rodenticide.

 Thus, a quantity of rodenticide bait comprising difethialone, having a persistence in the liver of rodents harmful target decreased relative to the hepatic persistence of difethialone, but a rodenticide efficacy sufficient to control rodents harmful target. The process according to the invention thus makes it possible to limit the secondary poisoning of non-rodent mammals and birds likely to preferentially consume the viscera-in particular the liver-of said dead or poisoned rodents, but including a reduced quantity-and in particular a non-lethal amount of difethialone.

 Advantageously and alternatively according to the invention, one chooses in combination:

 - the edible excipient;

 a proportion of each of the configuration stereoisomers of the difethialone relative to the difethialone, and

 - a mass proportion of the difethialone compared to the rodenticide bait, and;

 - a quantity of disseminated bait;

so that harmful target rodents consume a quantity of difethialone sufficient to be lethal to said harmful target rodents consuming said bait during a single period of 24 consecutive hours.

 A rodenticide bait according to this variant of the invention is a deadly bait in a single catch or "one-shot" in English. Advantageously and according to this variant of the invention, the mass proportion of difethialone in the rodenticide bait is between 5 and 200 ppm, especially between 5 ppm and 100 ppm, preferably between 5 ppm and 50 ppm, more preferably between between 15 ppm and 50 ppm.

 Advantageously and in another variant according to the invention, one chooses in combination:

 - the edible excipient;

 a proportion of each of the configuration stereoisomers of the difethialone relative to the difethialone, and

 - a mass proportion of difethialone compared to rodenticide bait;

so that harmful target rodents consume a quantity of difethialone;

 o non-lethal for harmful target rodents, that is, generally non-lethal to harmful target rodents, consuming said bait for a single 24-hour period, and;

 o sufficient to be lethal to harmful target rodents consuming said bait for several 24-hour periods, said periods being consecutive.

This other variant of the invention therefore also relates to a method for controlling harmful target rodents in which a quantity of lethal rodenticide bait is dispersed for harmful target rodents consuming this rodenticide bait and generally non-lethal for rodents or animals. non-targets accidentally consuming this rodenticide bait. This is called a "multi-dose" or "multi-feeding" control method. In such a method according to the invention, the consumption of rodenticide bait by a rodent harmful target for a period of 24 hours is insufficient to cause death of said rodent, while repeated consumption of rodenticide bait for at least two consecutive days can result in death of the target rodent.

 This other variant of the invention therefore aims at a method for controlling a population of harmful target rodents in which harmful rodent rodents are provided with a quantity of rodenticide bait that can be ingested by the target harmful rodents, the amount of rodenticide bait being sufficient to kill harmful target rodents consuming said rodenticide bait for several days.

 Advantageously, the quantity of disseminated rodenticide bait, the mass proportion of difethialone in the rodenticide bait and the proportion of each configuration stereoisomer of the difethialone in the difethialone are advantageously adapted so that the consumption of the rodenticide bait is lethal to harmful target rodents consuming bait daily for at least 2 24-hour periods, in particular 3 to 7 periods, said periods being consecutive.

 Advantageously and in this other variant according to the invention, the mass proportion of difethialone is between 5 ppm and 50 ppm, in particular between 5 ppm and 30 ppm - in particular of the order of 15 ppm - relative to the rodenticide bait.

 In a method according to the invention, harmful target rodents are provided with a quantity of rodenticide bait comprising difethialone of low hepatic persistence in harmful target rodents, the amount of rodenticide bait being sufficient to satisfy the daily appetite. harmful target rodents, said rodenticide bait comprising an amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone such that the ratio of that amount to the amount of the difethialone is less than 10%.

In a process according to the invention, the amount of disseminated rodenticide bait, the proportion of each configuration stereoisomer of difethialone relative to difethialone and the proportion mass of difethialone compared to rodenticide bait so as to allow consumption of rodenticide bait for several days by harmful target rodents, while limiting:

 - the risk of primary intoxication of mammals and non-target birds likely to consume only occasionally and accidentally such rodenticide bait;

 the risks of secondary intoxication, for example predators of target rodents, likely to consume rodents-dead or alive-targets having ingested a quantity of said bait.

 The invention also relates to a chromatographic process for the separation of configuration stereoisomers from difethialone, in which:

 a column for high pressure liquid chromatography of dimensions 150 × 2 mm and comprising a chiral stationary phase constituted by tris (4-methylbenzoate) cellulose particles, said particles having an average size of 3 μπι and having a size average of 1000 Å pore;

 a mixture of acetonitrile (A) and water comprising 0.1% by volume of formic acid (B) is chosen as liquid mobile phase, with an A / B volume ratio of 80/20; and with a flow rate of the liquid mobile phase in the chromatography column of 0.25 mL / min;

 a separation of the configuration stereoisomers of the difethialone at room temperature during which;

 a liquid composition comprising difethialone is introduced at the top of the column for chromatography, and then;

 the liquid composition is entrained with the mobile phase in the column for chromatography under conditions suitable for separating the configuration stereoisomers from the difethialone, and then;

at least one fraction of the mobile phase comprising a stereoisomer of configuration of the difethialone separated from the other stereos is collected. configuration isomer of the difethialone distinct from the collected configuration stereo-isomer, and;

 the liquid mobile phase of said collected fraction is removed so as to obtain the configuration stereoisomer of the collected difethialone.

 The invention also relates to a configuration stereoisomer of the isolated difethialone obtained by a process according to the invention.

 The invention also relates to a configuration stereoisomer of difethialone, a process for obtaining such a configuration stereoisomer of difethialone, a composition and a rodenticide bait comprising such a configuration stereoisomer, and a method of controlling harmful target rodents characterized in combination by all or some of the characteristics mentioned above or hereafter.

 Other objects, features and advantages of the invention will appear on reading the following description and examples given solely by way of non-limiting example and which refer to the appended figures, in which:

 FIG. 1 is relative to the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone; FIG. 1 a) represents a high-pressure liquid chromatographic analysis on a chiral column of the stereoisomers of configuration of difethialone (top) and the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone (bottom) - Figure b1) represents a circular dichroism spectrum of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone - Figure cl) is spectrum by 500 MHz proton NMR of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone;

FIG. 2 is relative to the laevorotatory enantiomer of said hetero-stereoisomer of difethialone (FIG. a2) represents a high-pressure liquid chromatographic analysis on a chiral column of the stereoisomers of configuration of difethialone (top) and the laevorotatory enantiomer of said hetero-stereoisomer of difethialone (bottom) - Figure b2) represents a circular dichroism spectrum of the levorotatory enantiomer of said hetero-stereoisomer of difethialone - Figure c2) is spectrum by proton NMR at 500 MHz of the levorotatory enantiomer of said hetero-stereoisomer of difethialone;

FIG. 3 relates to the dextrorotatory enantiomer of said homo-isomer of difethialone (FIG. a3) represents a high-pressure liquid chromatographic analysis on a chiral column of the stereoisomers of configuration of difethialone (top) and the dextrorotatory enantiomer of said difethialone homo-isomer (bottom) - Fig. b3) represents a circular dichroism spectrum of the dextrorotatory enantiomer of said difethialone homo-isomer - Fig. c3) is spectrum by 500 MHz proton NMR of the dextrorotatory enantiomer of said homo-stereoisomer of difethialone, and;

 FIG. 4 is relative to the laevorotatory enantiomer of said homo-isomer of difethialone; FIG. a4 represents a high-pressure liquid chromatography analysis on a chiral column of difethialone configuration stereoisomers (top); and the laevorotatory enantiomer of said homo-stereoisomer of difethialone (bottom) - Figure b4) represents a circular dichroism spectrum of the levorotatory enantiomer of said homo-stereoisomer of difethialone - Figure c4) is spectrum by 500 MHz proton NMR of the levorotatory enantiomer of said homo-stereoisomer of difethialone. A. Purification of configuration stereoisomers of difethialone

 A. L. Identification of said homo-stereoisomer of difethialone and said hetero-stereoisomer of difethialone

The homo-stereoisomer of difethialone is identified by magnetic resonance spectroscopy (1 H NMR) of the proton. The homo-stereoisomer of the difethialone in solution in CDCl ₃ has a multiplet with a chemical shift (δ) of between 4.9 ppm and 5.1 ppm and corresponding to the proton carried by the carbon 1 of the group 1,2 3,4-tetrahydronaphthalene of difethialone as shown in Figures c3) and c4).

The hetero-stereoisomer of difethialone is identified by its proton NMR spectrum made in CDCt ₃ , on which the chemical displacement of the proton carried by carbon 1 of the 1,2,3,4-tetrahydronaphthalene group of said hetero-stereoisonium. isomer of difethialone is of the order 5.3 ppm.

 A.2. Separation of the levorotatory and dextrorotatory enantiomers of said homo-isomer and said hetero-stereoisomer of difethialone by high pressure liquid chromatography

The inventors have solved the complex and unresolved problem to date of the separation of the levorotatory and dextrorotatory enantiomers of said hetero-stereoisomer from difethialone and of the levorotatory and dextrorotatory enantiomers of said homo-stereoisomer of difethialone from a difethialone composition predominantly in the form of said hetero-stereoisomer. They succeeded in separating the configuration stereoisomers of the difethialone by high performance liquid chromatography (high performance) on a chiral column LUX ^® Cellulose-3 (phenomenex, Le Pecq, France) of dimension 150 x 2 mm and comprising a chiral stationary phase consisting of porous cellulose particles tris (4-methylbenzoate), a particle size of 3 μπι and a porosity of 1000 A and using, as a mobile phase, an eluent formed of a mixture of acetonitrile (A) and water comprising formic acid in a volume proportion of 0.1% in water (B) with a volume ratio A / B of 80/20. The flow rate of the mobile phase in the column is 0.25 ml / min and the separation is carried out at a temperature of 23.2 ° C. The solution containing the sample to be analyzed is at a concentration of 1 μg of difethialone per milliliter of acetonitrile and is filtered on a regenerated cellulose membrane with a 0.2 μπι cutoff. The volume injected on the column is 1 μL ·.

In a process for separating the enantiomers of said homo-stereoisomer from difethialone, it is possible to detect said enantiomers at the outlet of the high-pressure liquid chromatography column by tandem mass spectrometry (MS / MS) in negative ionization mode. by electrospray (ESI, "ElectroSpray Ionization"). The nebulizer gas temperature is 350 ° C and its flow rate is 8 L / min. The nebulizer gas pressure is raised to 2700 hPa. In particular, MRM (Multiple Reaction Monitoring) transitions m / z 537.1 → 151.0 and m / z 537.1 → 78.9 corresponding to the signals of the difethialone are detected. Figures al), a2), a3) and a4) illustrate the separation of configuration stereoisomers from difethialone.

 In these experimental conditions:

 the value of the retention time (ti) of the laevorotatory enantiomer of said homo-stereoisomer is of the order of 8.1 min, as represented in FIG.

the value of the retention time (t ₂ ) of the laevorotatory enantiomer of said hetero-stereoisomer of difethialone is of the order of 9.4 min, as represented in FIG. a2);

the value of the retention time (t ₃ ) of the dextrorotatory enantiomer of said hetero-stereoisomer of difethialone is of the order of 11.7 min, as represented in FIG.

the value of the retention time (t ₄ ) of the dextrorotatory enantiomer of said homo-stereoisomer according to the invention is of the order of 14.4 min, as represented in FIG.

so that the configuration stereoisomers of the difethialone can be separated by high pressure liquid chromatography on a chiral column. Thus, under these experimental conditions, the elution order of the configuration stereoisomers of the difethialone is such that ti <t ₂ <t ₃ <t ₄ .

 The inventors have furthermore observed that it is possible to perform a preparative purification of each enantiomer of said homo-stereoisomer and of said hetero-stereoisomer of difethialone by preparative column chromatography of larger dimensions, in particular of a diameter. of 20 mm, comprising a chiral stationary phase consisting of porous particles of tris (4-methylbenzoate) cellulose with a particle size greater than 3 μπι and under conditions similar to those described for analytical chromatography.

It is possible to measure the amount of each configuration stereoisomer of difethialone by evaluating the area under the peak of the chromatogram corresponding to each configuration stereoisomer and, if appropriate, by comparing this area measurement with the areas obtained by analysis of samples comprising known amounts of stereoisomers of configuration of the difethialone.

 B. Structural characterization

 B.l. UV spectroscopy

 The UV spectrum of the dextrorotatory and laevorotatory enantiomers of said ho-stereo-isomer and said hetero-stereoisomer of difethialone in chloroform solution has absorbance peaks centered at 238.2 nm and 259.5 nm.

 B.2. Rotating power

 The inventors have characterized the dextrorotatory and laevorotatory enantiomers of said homo-stereoisomer and said hetero-stereoisomer of difethialone in the isolated state by their rotatory power (also called optical activity or circular birefringence), that is to say by its property to deflect the polarization plane of a polarized light. A deflection of the plane of polarization of the polarized light in the clockwise direction of rotation by facing the polarized light beam characterizes a dextrorotatory solution, and a deflection of the plane of polarization of the polarized light in the anticlockwise direction of rotation facing the Polarized light beam characterizes a solution and a levorotatory compound.

The rotatory power of a solution of a configuration stereoisomer of difethialone in chloroform is measured. The rotary power of this solution is measured by means of a P 2000 digital polarimeter (JASCO, Bouguenais, France) operating with excitation light with a wavelength of 589 nm. The average rotatory power obtained is calculated on two series of ten different measurements and the specific rotation power at 25 ° C. [a] ^{25 ° C.} 589 nm of each configuration stereoisomer of the difethialone in solution in chloroform, measured on the line D sodium (589 nm). The results are given in Table 1 below.

 Table 1

 Circular Dichroism

The circular dichroism spectrum of each dextrorotatory and laevorotatory enantiomer of said homo-stereo-isomer and said hetero-stereoisomer of the isolated difethialone reflects the difference in absorbance (AA = A _G -A _D ) of the two left circular polarization waves. (PCG) of intensity A _G and right circular polarization (PCD) of intensity A _D. It makes it possible to distinguish between the dextrorotatory and laevorotatory enantiomers of said homo-stereoisomer and of said hetero-stereoisomer of difethialone. This difference in absorbance of the two circular polarization waves is measured in a J-815 circular dichroism spectrometer (JASCO, Bouguenais, France). 2 ml of solution of each configuration stereoisomer of difethialone in methanol at the concentration given in Table 2 are prepared. The solution is transferred to a quartz cuvette for spectrophotometer. The circular dichroism spectrum of the solution is measured at 25 ° C. between 163 nm and 900 nm.

Table 2 C. Extraction of difethialone from difethialone-treated rat liver for the analysis of difethialone configuration stereoisomers

 Cl. Homogenization of the liver sample

0.525 g (± 0.025 g) of rat liver are weighed accurately and placed in a 50 ml polypropylene tube. 10 mL of acetone was added and the suspension is subjected to homogenization using a homogenizer / disperser ^® Ultra-Turrax for a period of about 30 sec. The rod of the homogenizer / disperser is rinsed with hot water and then twice with 20 ml of acetone in a polypropylene tube. The homogenate is centrifuged for 5 minutes at a centrifugation rate of 3000 rpm (rotation per minute). The supernatant is collected and decanted into a test tube. The sample is evaporated under a stream of nitrogen (N ₂ ) at a temperature of 40 ° C to form a dry extract.

 C.2. Elimination of lipids

In the tube containing the dry extract, 1 mL of acetonitrile is added so as to solubilize the dry extract. The acetonitrile solution is washed twice in succession with 1 mL of hexane. The lipid-freed extract is dried under a flow of nitrogen (N ₂ ) at a temperature of 40 ° C., then taken up with 0.5 ml of methanol and solubilized by vortexing. 0.5 ml of ultrapure water (Milli-Q) is then added. The sample is homogenized under a vortex.

 C.3. Extraction of Solid Phase Extraction (SPE)

1 ml of dichloromethane is passed, then 1 ml of methanol, then 1 ml of ultrapure water (Milli-Q) on an Oasis HLB lcc cartridge (WAT094225, Waters). The lipid-free liver extract (1 ml of MeOH / H ₂ O Milli-Q) containing the difethialone at the top of the cartridge is then deposited so that the liver extract enters the cartridge by gravity in contact with the cartridge. the solid phase. At the top of the cartridge is deposited 1 ml of washing solution formed of methanol and ultrapure water in a volume proportion of 90/10. The cartridge is dried by vacuum suction connected at the bottom of the cartridge. 1 mL of elution solution consisting of dichloromethane and methanol in a volume proportion of 90/10 is then deposited at the top of the cartridge and an eluate comprising difethialone is collected at the bottom of the cartridge. The solvent of the eluate is evaporated under a flow of nitrogen (N ₂ ) at a temperature of 40 ° C. The sample is taken up in 0.5 mL of acetonitrile and the acetonitrile solution containing the difethialone is filtered on a 0.2 μπι filter.

 The composition is analyzed by high pressure liquid chromatography on a chiral column as described in point A2) above. D. Study of Hepatic Persistence of Difethialone Configuration Stereoisomers in Rats

 By gavage ("per os") to 8-week-old, male-female rats (Rattus norvegicus male and female) sensitive to coumafen weighing about 200 g, a solution of a mixture of homo-steroids isomer (DFN-Homo-SI) and hetero-stereoisomer (DFN-hetero-SI) of difethialone in a mixture of vegetable oil and 5-DMSO. The molar proportion of homo-stereoisomer is 40% and the molar proportion of hetero-stereoisomer is 60%. Each configuration stereoisomer of difethialone is formed from a racemic mixture of the two enantiomers of said corresponding configuration stereo-isomer.

 On D0, each rat is administered gavage solution so that the amount of difethialone ingested by each rat is of the order of 3.4 mg per kilogram of rat. To avoid hemorrhage, the rats are also treated daily by subcutaneous administration of a dose of vitamin K1 (as antidote to bleeding) at a rate of 0.1U per 200g of rat's weight.

At 4 hours (H + 4), 9 hours (H + 9), 24 hours (H + 24), 120 hours (H + 120), 168 hours (H + 168) and 216 hours (H + 216) after the 3 male rats and 3 female rats previously anesthetized with isoflurane are euthanized, the liver is taken from the euthanized rats and the difethialone is then extracted from the liver and the amount of each of the stereoisomers of the difethialone configuration is measured. measurement of the area under the peaks of the chromatogram obtained and each configuration stereo-isomer is quantified by comparison with a calibration curve. We dose:

 the dextrorotatory enantiomer of said homo-stereoisomer ("DFN-Homo-dextro");

the levorotatory enantiomer of said homo-stereoisomer ("DFN-Homo-lévo"); the dextrorotatory enantiomer of said heterois stereoisomer ("DFN-hetero-dextro");

the laevorotatory enantiomer of said hetero-stereoisomer ("DFN-hetero-lévo"); present in the liver of gaved rats.

 The results are given in the following Table 3 in which each value is the average of the levels measured on 6 rats (3 male and 3 female rats) and expressed in nano-grams of enantiomer per gram of liver (ng / g).

 Table 3

 The dextrorotatory enantiomer of said hetero-stereoisomer of difethialone is the most persistent in the liver of harmful target rodents.

 Rodenticide bait comprising a mass proportion of

14.7 ppm of difethialone

A pasty rodenticide bait according to the invention is produced by dispersing a quantity of dextrorotatory enantiomer of said homo-stereoisomer of difethialone in an edible excipent comprising grease. vegetable and cereal flour. The measured proportion of difethialone relative to the bait is 14.7 ppm (14.7 mg of difethialone per kilogram of bait) and the proportion of dextrorotatory enantiomer of said ho-stereo-isomer relative to the difethialone is 99.7%. The bait further comprises a mass proportion of 0.3% laevorotatory enantiomer of said hetero-stereoisomer of difethialone relative to difethialone. The rodenticide bait according to the invention is substantially free of dextrorotatory enantiomer of said hetero-stereoisomer of difethialone.

 On D0, ten male-female Sprague Dawley rats (SD, 5 male and female rats) were placed in individual cages with a reference diet free of rodenticide. On D3, each rat is weighed and then 50 g of rodenticide bait as described above are made available to each rat. This supply of 50 g of rodenticide bait is renewed daily. The bait consumed by the rats is supplemented with 50 g of bait on D4, D5 and D6. As of J7, residual rodenticide baits are discarded and a rodenticide free diet is provided to all rats. The rats are monitored for 3 weeks.

 The average amounts of bait consumed daily by a rat on D4, D5, D6 and D7 expressed in grams per day are given in Table 4 below.

 Table 4

 It should be noted that no rat consumed a daily amount of bait less than 1 g / day. All rats (100%) die between D9 and D10. The mortality is 100% at D10.

The bait dosed at 14.7 ppm of difethialone (of which 99.7% dextrorotatory enantiomer of said homo-stereoisomer of difethialone) allows Achieving a 100% mortality rate while minimizing the risk of secondary intoxication of animals - including susceptible predators or scavengers of weakened target rodents that have consumed a rodenticide bait.

 It goes without saying that the invention can be the subject of many variants and applications. In particular, a composition, a rodenticide bait and a method for controlling harmful target rodents are subject to infinity of variants both in the formulation of the bait and in the methods of implementation of the method.

Claims

 1 / - Composition comprising difethialone, characterized in that it comprises a difethialone configuration stereoisomer, called hetero-stereoisomer, of formula 3- (4'-bromobiphenyl-4-yl) -1- ( 4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of distinct absolute configurations, said composition comprising an amount of dextrorotatory enantiomer of said hetero-stereoisomer such that the ratio of this amount to the amount of the difethialone in the composition is less than 10%; the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the composition being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the composition.  21 - Composition according to claim 1, characterized in that it comprises an amount of levorotatory enantiomer of a configuration stereoisomer difethialone, said homo-stereoisomer, of formula 3- (4'-bromobiphenyl- 4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of the same absolute configuration (1S, 3S or 1R, 3R), the amount of said laevorotatory enantiomer of said homo-isomer in the composition being such that the ratio of this amount to the total amount of the difethialone in the composition is less than 10%.  3 / - Composition according to one of claims 1 or 2, characterized in that it comprises an amount of levorotatory enantiomer of said hetero-stereoisomer of the difethialone in the composition such that the ratio of this amount to the total amount difethialone in the composition is less than 10%. 4 / - Composition according to one of claims 2 or 3, characterized in that it comprises an amount of dextrorotatory enantiomer of said homo-stereoisomer of difethialone such as the ratio of this amount on the total amount of the difethialone in the composition is between 10% and 100%.  5 / - Rodenticide bait comprising difethialone and at least one edible carrier for harmful target rodents, characterized in that it comprises a stereoisomer of configuration of difethialone, called hetero-stereoisomer, of formula 3- (4 3-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of distinct absolute configurations, the rodenticide bait comprising a dextrorotatory enantiomer amount of said heterois stereoisomer such that the ratio of this amount to the amount of the difethialone in the rodenticide bait is less than 10%; the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait.  6 / - rodenticide bait according to claim 5, characterized in that it comprises a configuration stereoisomer of the diféthialone, said homo-stereoisomer, of formula 3- (4'-bromobiphenyl-4-yl) -l - (4-hydroxythiocoumarin-3-yl) -1,2,3,4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of the same absolute configuration, the rodenticide bait comprising an amount of a levorotatory enantiomer of said difethialone homo-isomer, such that the ratio of the amount of laevorotatory enantiomer of said difethialone homo-isomer to the total amount of the difethialone in the rodenticide bait is less than at 10%. Il - rodenticide bait according to one of claims 5 or 6, characterized in that it comprises an amount of a levorotatory enantiomer of said hetero-stereoisomer of difethialone such as the ratio of the amount of the laevorotatory enantiomer of said hetero-stereoisomer of difethialone in rodenticide bait on the total amount of difethialone in the rodenticide bait is less than 10%. 8 / - rodenticide bait according to one of claims 5 to 7, characterized in that the edible carrier comprises at least one food selected from the group consisting of cereal seeds, cereal seed mills, cereal seed meal, cereal seed flakes, cereal bran and non-cereal seeds.  91 - Rodenticide bait according to one of claims 5 to 8, characterized in that it comprises a mass quantity of difethialone such that the ratio of this mass quantity of difethialone to the mass quantity of the rodenticide bait is less than 200 ppm.  10 / - A method of controlling harmful target rodents, wherein a quantity of rodenticide bait comprising difethialone is dispersed, and  at least one edible carrier for harmful target rodents, and  a configuration hetero-isomer of the hetero-stereoisomer difethialone of formula 3- (4'-bromobiphenyl-4-yl) -1- (4-hydroxythiocoumarin-3-yl) -1,2,3 , 4-tetrahydronaphthalene, wherein the carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group are of distinct absolute configurations, the rodenticidal bait comprising an amount of a dextrorotatory enantiomer of said hetero-stereoisomer such as the ratio of this quantity to the amount of difethialone in the rodenticide bait is less than 10%; the amount of the dextrorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait being different from the amount of laevorotatory enantiomer of said hetero-stereoisomer of the difethialone in the rodenticide bait.  11 / - Method according to claim 10, characterized in that in combination:  - the edible excipient; a proportion of each of the configuration stereoisomers of the difethialone relative to the difethialone, and - a mass proportion of difethialone compared to the rodenticide bait, and;  - a quantity of disseminated bait; so that harmful target rodents consume a quantity of difethialone sufficient to be lethal to said harmful target rodents consuming said bait during a single 24-hour period.  12 / - Method according to claim 10, characterized in that in combination:  - the edible excipient;  a proportion of each of the configuration stereoisomers of the difethialone relative to the difethialone, and  - a mass proportion of difethialone compared to rodenticide bait; so that harmful target rodents consume a quantity of difethialone;  o non-lethal for harmful target rodents consuming said bait for a single 24-hour period, and;  o sufficient to be lethal to harmful target rodents consuming said bait for several 24-hour periods, said periods being consecutive.  13 / - Chromatographic process for separating stereoisomers from the configuration of difethialone, in which:  a column for high pressure liquid chromatography of dimensions 150 × 2 mm and comprising a chiral stationary phase constituted by tris (4-methylbenzoate) cellulose particles, said particles having an average size of 3 μπι and having a size average of 1000 Å pore; a mixture of acetonitrile (A) and water comprising 0.1% by volume of formic acid (B) is chosen as liquid mobile phase, with a volume ratio A / B of 80/20 and with a flow rate of the mobile liquid phase in the chromatography column of 0.25 ml / min;  a separation of the configuration stereoisomers of the difethialone at room temperature during which;  a liquid composition comprising difethialone is introduced at the top of the column for chromatography, and then;  the liquid composition is entrained with the mobile phase in the column for chromatography under conditions suitable for separating the configuration stereoisomers from the difethialone, and then;  collecting at least one fraction of the mobile phase comprising a configuration stereoisomer of the difethialone separated from the other configuration stereoisomers of the difethialone distinct from the collected configuration stereoisomer, and;  the liquid mobile phase of said collected fraction is removed so as to obtain the configuration stereoisomer of the collected difethialone.